Phytic acid/chitosan-assisted zwitterionic double-network hydrogels with enhanced mechanical properties, adhesion...

Ionic conductive hydrogels have recently attracted tremendous attention in flexible wearable strain sensors. However, achieving a combination of good mechanical properties, strong adhesion to various material surfaces, and remarkable ionic conductivity in a single ionic conductive hydrogel remains a challenge. Herein, new poly(acrylamide-co-sulfobetaine methacrylate)/chitosan/phytic acid (ASCP) ionic conductive hydrogels with double networks were prepared through free radical polymerization. The versatile functional groups from chitosan and phytic acid gave the hydrogels universal adhesion capabilities with a maximum adhesion strength of 18.7 kPa to paper. The obtained ASCP conductive hydrogels exhibited a large elongation of 675 % and a moderate tensile strength 52.8 kPa due to the synergy of chemical cross-linking and physical interactions. Phytic acid as the conductive component conferred the hydrogels with excellent ionic conductivity of 10.3 S m^-1. Moreover, the incorporation of chitosan and phytic acid imparted the hydrogels with enhanced anti-drying capability, as evidenced by a residual mass ratio of 58.3 % after 10 days, and exhibited favorable anti-swelling behavior, with an equilibrium swelling ratio of 115 % in water after 4 days. The described ionic conductive hydrogels were assembled into wearable strain sensors to detect various human joint movements. This work offers a straightforward strategy to design multifunctional conductive hydrogels which envision prospective applications in wearable sensors and other flexible electronic devices.